1. Field of the Invention
The present invention generally relates to a low noise block down converter. More particularly, the present invention relates to a low noise block down converter utilized for a satellite reception system.
2. Description of the Background Art
In a conventional Low Noise Block down converter (hereinafter referred to as an “LNB”) with a plurality of local oscillators, each local oscillator is completely separated from another local oscillator by a metal wall in order to prevent electromagnetic coupling between a dielectric resonator in each local oscillator and a dielectric resonator in another local oscillator.
FIGS. 7A and 7B are cross-sectional views showing a main portion of the conventional LNB. FIG. 7A is a cross-sectional view cut along a line VIIA—VIIA in FIG. 7B, while FIG. 7B is a cross-sectional view cut along a line VIIB—VIIB in FIG. 7A.
In FIGS. 7A and 7B, two local oscillators 41a and 41b of the LNB are respectively housed within shielding chambers 40a and 40b in a metal shielding box 40, and are electromagnetically shielded by a metal wall 40c. Local oscillator 41a includes a dielectric resonator 42a, an oscillation device 43a, a microstrip line 44a, and a substrate 45a. Local oscillator 41a outputs a signal of a certain frequency (e.g. 9.75 GHz). Local oscillator 41b includes a dielectric resonator 42b, an oscillation device 43b, a microstrip line 44b, and a substrate 45b. Local oscillator 41b outputs a signal of another frequency (e.g. 10.6 GHz). In FIG. 7B, dashed circles show electromagnetic fields radiated from dielectric resonators 42a and 42b. 
As described above, in the conventional low noise block down converter, metal shielding box 40 is divided by metal wall 40c to prevent electromagnetic coupling between dielectric resonators 42a and 42b. Therefore, downsizing of metal shielding box 40 and hence the low noise block down converter has been difficult to achieve.